1. Field of the Invention
The present invention relates to a communication system having a service handoff function, and a user terminal device, transfer destination terminal device and a proxy server device for configuring the communication system.
2. Description of the Related Art
In recent years, various forms of ubiquitous computing environments, in which a computer can be utilized everywhere without being conscious of using the computer, have been considered.
For example, places or facilities called hot spots, where network connection from information equipment owned by a user is enabled even if the user is out, have already been put in practical use, and in such places, connection services utilizing wireless LAN or the like are provided. Furthermore, coffee shops, special shops, etc. where terminals connected to the Internet are set up are opened on a global basis, and can be utilized with ease.
Not limited to the above-described cases, if the user can freely utilize many devices that exist here and there in the neighborhood, such as a computer at a place where the user goes out, the user can receive various communications and services flexibly. In order to utilize the nearby devices, there needs a technique by which the devices are discovered and an optimal one is selected to receive a target service through the device.
For example, there are a PDA and a portable telephone as a portable terminal that a user can carry, which have been rapidly enhanced in performance in recent years, so that e-mail exchanges, WEB browsing and the like are enabled. However, wireless networks utilized by the portable terminal are far less stable and their communication bands are smaller in comparison with connection through wired networks. Moreover, as compared with a fixed terminal whose power source is connected, a portable terminal has processing capacity limited to a lower level due to its size and electric power saving, and has only small-sized simple user interface mounted. Its display ability cannot compare with that of the fixed terminal connected to a large screen display.
Consequently, in order that highly functional devices in the neighborhood can also be freely utilized instead of depending on such portable terminals only, various architectures as described in Publicly Known Literatures 1 to 4 have been proposed.
As related art techniques, there are proposed two architectures: architecture using a proxy and end-to-end type architecture.
Such an end-to-end type architecture as described in Publicly Known Literature 2 is well-known, in which a communication application for executing handoff between terminals is also installed in a correspondent node performing delivery to provide end-to-end mobility support.
Therefore, it is impossible that an existing communication application other than the above-described communication application is handed over between terminals, that the handoff between terminals is executed in communication with a correspondent node which does not have the application for handoff, or the like.
Furthermore, as proxy type architecture, there is proposed Medler in Publicly Known Literature 5, MSOCKS in Publicly Known Literature 6, or the like. However, these do not support seamless handover between terminals.
Furthermore, although MPA proposed in Publicly Known Literature 7, and Universal Inbox of Publicly Known Literature 8 realize an architecture which enables an optimal device for receiving to be selected adaptably, these have not realized seamless device switching, either.
As a method in which the handoff between devices with a proxy type configuration is realized, there is proposed a method (Publicly Known Literature 9) in which an interface such as a display of a portable telephone is transferred to a nearby device, thereby succeeding in solving the insufficiency in user interface of a portable terminal.
However, the solution of the problem with the insufficiency in processing capacity of the portable terminal has not been realized, yet.